Method and system for transmiting data and for determining the transmission properties in a radio communications system

ABSTRACT

Method and arrangement for transmitting data and for determining the transmission characteristics in a radiocommunications system.  
     A possibility for transmitting data via a radiolink with a timeslot structure in a radiocommunications system is described, measurement data (MA) for determining the transmission characteristics of the radiolink being inserted within the timeslot structure in dependence on the variation with time of the transmission characteristics of the radiolink between the base station (BS) and the terminal (MS) at the subscriber end in the timeslot structure.

[0001] Method and arrangement for transmitting data and for determining the transmission characteristics in a radiocommunications system

[0002] The present invention relates to a method and an arrangement for transmitting data and for examining the transmission characteristics in a radiocommunications system.

[0003] In radiocommunications systems, data like signaling data, voice data or other user data are transmitted with the aid of electromagnetic waves via a radio interface between the transmitting and the receiving device, at least in a part-area of the communications system. An example of current radiocommunications networks are networks according to the GSM standard and with a TDMA transmission method which are operated at carrier frequencies of 900, 1800 or 1900 MHz. Another example are future radiocommunications systems such as UMTS which is based on a CDMA, TD/CDMA or TDD transmission method and uses carrier frequencies in the range of approx. 200 MHz. The data to be transmitted are transmitted at these carrier frequencies between base stations of the communications system at the network end and mobile or stationary terminals at the subscriber end.

[0004] Special radiocommunications systems are those which have a time slot structure. As a rule, the timeslots are combined in timeslot frames which, in turn, can be part of a higher-level frame structure. Examples of such radiocommunications systems with a timeslot structure are TDMA, TDD, TD/CDMA, TD/SDCDMA and FDD systems. In the case of a GSM system, for example, eight timeslots are combined in one timeslot frame. Each individual timeslot has a duration of 0.577 ms and the complete timeslot frame has a duration of about 4.6 ms.

[0005] In a TDD system in UMTS, in contrast, a timeslot frame has 16 timeslots which in each case have a duration of 625 μs. The complete timeslot frame has a duration of 10 ms. A part of the timeslots of a TDD timeslot frame is used for the uplink from the terminal at the subscriber end to the base station and the other part of the timeslots of the timeslot frame is used for the downlink from the base station to the terminal at the subscriber end. Between the timeslots of the uplink and the downlink, at least one switching point is inserted which can be shifted within the timeslot frame in order to provide for an asymmetric allocation of the timeslots to the uplink and to the downlink.

[0006] Within a timeslot, a data block or burst is transmitted with a particular predefined structure. Apart from payload data, the data block can also contain other data which are necessary or useful for the transmission of the payload data. Thus, for example, control or signaling data or particular measurement data such as, for example, for determining the transmission characteristics can be provided in these data blocks.

[0007] A major aim in radiocommunications systems is to provide the subscribers with the highest possible measure of comfort. In particular, the best possible quality of data transmission is to be guaranteed to the subscribers, on the one hand and, on the other hand, the highest possible data rate is to be provided by means of corresponding transmission capacity. These requirements represent an increasing problem especially with regard to the continuously growing numbers of subscribers in radiocommunications systems.

[0008] It is, therefore, the object of the present invention to provide a possibility for transmitting data and for determining transmission characteristics in a radiocommunications system which allows for the best possible quality of the data transmission and, at the same time, high transmission capacity.

[0009] This object is achieved by the features of present patent claims 1, 13, 14 and 15.

[0010] In the method according to the invention according to claim 1 for transmitting data via a radiolink with a timeslot structure in a radiocommunications system with at least one base station and at least one terminal at the subscriber end, measurement data for determining the transmission characteristics of the radiolink are provided within the timeslot structure. According to the invention, the measurement data are inserted into the timeslot structure in dependence on the variation with time of the transmission characteristics of the radiolink between the base station and the terminal at the subscriber end.

[0011] Thus, it is not necessary to continuously provide a particular set of the data, which can be transmitted altogether via the radiolink, for measurements of the transmission characteristics. Instead, the measurement data are inserted into the timeslot structure in accordance with the individual situations of the respective radiolink. If it can be seen that the individual situations of the radiolink are barely changing, a continuous transmission of measurement data for continuous checking of the transmission characteristics of the radiolink is not required. The volume of data necessary for the measurement data can thus be largely saved and provided for other data such as payload data or signaling data. This provides an increase in transmission capacity of the radiocommunications system without significantly impairing the quality of the radiolink.

[0012] It is possible to transmit one or more channels between the base station and the terminal over the radiolink between the base station and the terminal. Correspondingly, the determination of the transmission characteristics and the insertion or saving of measurement data dependent thereon can take place on the same channel or one channel can be used for determining the transmission characteristics and measurement data can be saved on one or more other channels in dependence thereon. The latter makes sense, e.g. if the surveying of a channel, for example of a signaling channel, already provides information on the transmission characteristics on the other channels, for example on traffic channels.

[0013] The transmission characteristics of the radiolink between the base station and the terminal at the subscriber end can be influenced by different quantities. Thus, the quality or the propagation times of the radiolink can change due to different factors. Examples of quantities influencing the radiolink which can vary with time and can thus affect a variation with time of the transmission characteristics are the location of the terminal at the subscriber end, namely in the case of a mobile terminal which can move at a particular relative speed with respect to the base station, or also external disturbances of the radiolink such as, for example, by meeting with other radiolinks or by shading due to moving objects such as, for example, passing vehicles. It can be provided for the variation with time of the quantities which influence the transmission characteristics to be determined in order to insert or save measurement data in dependence on the variation with time of these quantities.

[0014] If the variation with time of the location of the terminal at the subscriber end, in particular, is considered and particularly the relative speed between the base stations and the terminal at the subscriber end, it can be provided that measurement data are inserted into the timeslot structure when the relative speed exceeds a predetermined limit speed. As a result, the situation can be reached where basically no measurement data need to be transmitted during an existing radiolink especially in the case where terminals are not moving or moving only slowly. At particular times, however, measurement data can be transmitted once or several times in order to determine the transmission characteristics of the radiolink at least once. In particular, such a measurement can be made preferably at the beginning of a radiolink. This insertion of measurement data at the beginning of a radiolink can also be provided as standard for all other cases of radiolinks which are influenced by quantities which are variable with time. In this arrangement, the measurement data are inserted into a predetermined number of timeslots but in all other timeslots, measurement data are only inserted in dependence on the variation with time of the transmission characteristics or of the quantities influencing them.

[0015] In particular, it can be provided that the measurement data are inserted into an increasing number of timeslots of the timeslot structure with increasing variation with time of the transmission characteristics of the radiolink, particularly due to an increasing variation with time of the quantities influencing the transmission characteristics. The result is that the determination of the transmission characteristics is adapted to the extent of the variation with time of the transmission characteristics of the radiolink and it is possible to respond with a larger number of measurements to transmission characteristics which change more rapidly. Conversely, naturally, the measurement data can be inserted into a decreasing number of timeslots of the timeslot structure with a decreasing variation with time of the transmission characteristics of the radiolink or of the quantities influencing it.

[0016] Thus, if the influence on the radiolink with time decreases with time, the measurement data can be increasingly saved again and the released volume of data can be provided for other applications such as payload data or signaling data. In both cases, a certain hysteresis can be provided, i.e. the increased or reduced variation with time must have first stabilized over a particular period before the system responds with the insertion or saving of measurement data.

[0017] As already described above, the result is the interchangeability of measurement data, on the one hand, and payload data or signaling data, on the other hand. If a certain data area or a certain volume of data, respectively, is not needed for measurement data, it can be provided for payload data or signaling data as a result of which the transmission capacity of the radiolink can be increased. If it is found, however, that additional measurement data must be inserted into the timeslot structure, in order to be able to guarantee the quality of the link, for example, the measurement data are inserted into the timeslot structure instead of a particular part of the payload data or signaling data.

[0018] The present invention also comprises an arrangement for transmitting data via a radiolink with a timeslot structure as claimed in claim 12 which, in particular, is constructed for carrying out a method described above, the arrangement having devices for determining the variation with time of the transmission characteristics of the radiolink between the base station and the terminal at the subscriber end. These devices are coupled to devices for inserting measurement data into the timeslot structure.

[0019] A further subject matter of the present invention is a radiocommunications system according to claim 13 which exhibits at least one arrangement, described above, for transmitting data via a radiolink with a timeslot structure.

[0020] Finally, the present invention also comprises a base station for a radiocommunications system as claimed in claim 14 which exhibits an arrangement, described above, for transmitting data [lacuna] a radio link with a timeslot structure. In this case, it can be provided, for example, that the devices for determining the variation with time of the transmission characteristics are only constructed as evaluating devices which evaluate measurement results of another device, for example of a terminal at the subscriber end.

[0021] In the text which follows, a special exemplary embodiment of the present invention will be explained with reference to FIGS. 1 to [insert]. In the figures:

[0022]FIG. 1: shows a diagrammatic representation of a radiocommunications system according to the invention,

[0023]FIG. 2: shows a diagrammatic representation of a timeslot structure of a TDD system,

[0024]FIG. 3: shows a diagrammatic representation of a timeslot frame of the TDD system with measurement data,

[0025]FIG. 4: shows timeslot frames according to FIG. 3 but with payload data instead of the measurement data,

[0026]FIG. 5: shows timeslot frames according to FIG. 3 but with signaling data instead of the measurement data.

[0027]FIG. 1 shows a mobile radio system as an example of a radiocommunications system which exhibits a multiplicity of mobile switching centers MSC which are connected to one another and at least one of which forms an access to other communication networks such as, for example a landline network PSIN. In addition, the mobile switching centers MSC are connected to a device RNM for allocating resources in the mobile radio system to which various base stations BS are linked. Furthermore, the mobile radio system exhibits an operation and maintenance center OMC which is also connected to the RNM.

[0028] Apart from other functions, the base stations BS mainly exhibit a device for determining the transmission characteristics of radiolinks between the base station BS and the terminals MS at the subscriber end. In the present example, it is only constructed as an evaluating device since the actual measurement takes place at another location, namely in the terminal MS at the subscriber end. For this reason, the evaluating device of the base station BS is generally called BS Evaluation Unit in FIG. 1. The base station sends out a signaling channel BCCH (Broadcast Control Channel) which is detected and surveyed by the terminals at the subscriber end, for example by a mobile station MS. For this purpose, the terminal MS exhibits corresponding measuring devices which are generally called MS measuring unit in FIG. 1. Using these measuring devices, the terminal MS can determine the variation with time of the transmission characteristics of the radiolink. The corresponding results can be transmitted to the BS evaluation unit automatically or on request. In the base station, it would then be possible to determine, e.g. the relative speed between the terminal at the subscriber end and the base station from the results of the measurement. Depending on the results of the measurement, a device coupled to the BS measuring unit which is generally called the MA unit in FIG. 1, inserts measurement data MA (midamble) in a suitable form into the timeslot structure of a radiolink for the transmission of payload data. These payload data are transmitted on a separate channel, namely a traffic channel TCH. If it is found that the transmission characteristics of the radiolink scarcely change, the measurement data MA can be saved at least on the traffic channel, which data would be provided there as on the signaling channel BCCH.

[0029]FIG. 2 shows a timeslot structure of a TDD system in which a timeslot frame comprises 16 timeslots ts0 to ts15. In FIG. 1, the first eight timeslots ts0 to ts7 are allocated to the downlink and the remaining timeslots ts8 to ts15 after the switching point SP are allocated to the uplink. It is also possible to provide a number of switching points SP within such a timeslot frame and these switching points can be inserted into the timeslot frame at different locations.

[0030]FIG. 3 shows the structure of a data block (burst) which is transmitted within a timeslot. This data block comprises a first set of payload data D1 followed by measurement data MA, a second set of payload data D2 and control data GP for checking an error-free transmission of the payload data.

[0031] If the corresponding measuring devices in the radiocommunications system find that the transmission characteristics of the radiolink between the base station BS and the terminal MS at the subscriber end or, respectively, the quantities influencing them change only little with time, it is possible largely to dispense with the measurement data within the individual timeslots at least of the traffic channel TCH of the corresponding radiolink. This situation is shown in the further figures.

[0032]FIG. 4 shows a data block in which further payload data are transmitted instead of the measurement data MA. Thus, it is possible to transmit greater volumes of payload data D3, D4 within this data block than in the data block according to FIG. 3.

[0033]FIG. 5 shows an alternative to FIG. 4 where the measurement data of the data block from FIG. 3 have been replaced by additional signaling data SD which thus e.g. provide for in-band signaling.

[0034] As can be seen from FIGS. 4 and 5, the provision of measurement data within the timeslots of the corresponding link or at least in a part of the channels of the link can largely be dispensed with for the cases in which the transmission characteristics of the radiolink between the base station BS and the terminal MS or, respectively, the quantities influencing the transmission characteristics, change only a little as, for example, in the case of a mobile station MS which is moving only slowly or not at all. The consequence is a distinct increase in transmission capacity of the corresponding link. 

1. A method for transmitting data via a radiolink with a timeslot structure in a radiocommunications system with at least one base station (BS) and at least one terminal (MS) at the subscriber end, measurement data (MA) for determining the transmission characteristics of the radiolink being inserted within the timeslot structure, characterized in that the measurement data (MA) are inserted into the timeslot structure in dependence on the variation with time of the transmission characteristics of the radiolink between the base station (BS) and the terminal (MS) at the subscriber end.
 2. The method as claimed in claim 1, characterized in that a number of channels (BCCH, TCH) are provided for the radiolink and the determination of the transmission characteristics and the insertion of the measurement data (MA) take place on the same channel (BCCH, TCH).
 3. The method as claimed in claim 1, characterized in that a number of channels (BCCH, TCH) are provided for the radiolink and the determination of the transmission characteristics and the insertion of the measurement data (MA) take place on different channels (BCCH, TCH).
 4. The method as claimed in one of claims 1 to 3, characterized in that in the determination of the variation with time of the transmission characteristics, the variation with time of quantities influencing the transmission characteristics is determined.
 5. The method as claimed in claim 4, characterized in that the measurement data (MA) are inserted into the timeslot structure in dependence on external disturbances of the radiolink between the base station (BS) and the terminal (MS) at the subscriber end.
 6. The method as claimed in claim 4, characterized in that the measurement data (MA) are inserted into the timeslot structure in dependence on the relative speed between the base station (BS) and the terminal (MS) at the subscriber end.
 7. The method as claimed in claim 6, characterized in that the measurement data (MA) are inserted into the timeslot structure as soon as the relative speed between the base station (BS) and the terminal (MS) at the subscriber end exceeds a predetermined limit speed.
 8. The method as claimed in one of claims 1 to 7, characterized in that measurement data (MA) are inserted into an increasing number of timeslots (ts0-ts15) of the timeslot structure within increasing variation with time of the transmission characteristics of the radiolink.
 9. The method as claimed in one of claims 1 to 8, characterized in that measurement data (MA) are inserted into a decreasing number of timeslots (ts0-ts15) of the timeslot structure with decreasing variation with time of the transmission characteristics of the radiolink.
 10. The method as claimed in one of claims 1 to 9, characterized in that measurement data (MA) are always inserted into a predetermined number of timeslots (ts0-ts15) at the beginning of a radiolink.
 11. The method as claimed in one of claims 1 to 10, characterized in that when the measurement data (MA) are inserted into the timeslots, the measurement data (MA) are inserted into the timeslots (ts0-ts15) instead of payload data (D1-D6) or signaling data (SD).
 12. The method as claimed in one of claims 1 to 11, characterized in that the measurement data (MA) are in each case inserted into the timeslots (ts0-ts15) as a preamble or midamble.
 13. An arrangement for transmitting data via a radiolink with a timeslot structure, particularly for carrying out a method as claimed in one of claims 1 to 11, characterized in that the arrangement exhibits devices for determining the variation with time of the transmission characteristics of the radiolink between the base station (BS) and the terminal (MS) at the subscriber end, which are coupled to devices for inserting measurement data (MA) into the timeslot structure in dependence on the variation with time of the transmission characteristics of the radiolink.
 14. A radiocommunications system having at least one arrangement as claimed in claim
 13. 15. A base station for a radiocommunications system having an arrangement as claimed in claim
 13. 16. The base station as claimed in claim 15, characterized in that the devices for determining the variation with time of the transmission characteristics are constructed as evaluating devices for evaluating measurement results of an external device, particularly of a terminal at the subscriber end. 